The present invention relates to a digital transmitter and a method for compensating mismatch in a digital transmitter, and more particularly to a low noise and low cost digital transmitter and related compensation method.
In wireless communication system, using a digital transmitter to digitally amplify and transmit RF (Radio Frequency) signal can be the most area saving and power efficient way. Conventionally, there have two ways to implement the digital transmitter. The first type is thermo-coding, and the second type is binary-coding. For the thermo-coding digital transmitter, the output power is a combination of a plurality of unit powers outputted by a plurality of unit cells. Therefore, a thermo-coding digital transmitter may need a lots of unit cells to generate a high power output signal. On the other hand, the binary-coding digital transmitter uses a plurality of binary-coding cells to generate an amplified output signal. The number of the binary-coding cells is less than the number of unit cells of the thermo-coding digital transmitter because the binary-coding cell may generate power higher than the unit power of the thermo-coding digital transmitter. The areas of the binary-coding cells should be well-defined to output their corresponding powers. In practical, however, the semiconductor process may somehow cause the mismatch occurs in the unit cells or binary-coding cells, and consequently affect the performance of the digital transmitter.
Therefore, how to solve the cell mismatch problem of a digital transmitter is an urgent problem in the field of wireless communication system.